The Reciprocal Relationship Between Lumbar Intervertebral Disk Degeneration and the MRI-based Vertebral Bone Quality Score

Abstract

Study Design. Retrospective longitudinal study. Objective. To investigate the association between lumbar intervertebral disk degeneration (DD) and the vertebral bone quality (VBQ) score. Background. The VBQ score that is based on magnetic resonance imaging has been proposed as a measure of lumbar spine bone quality and is a significant predictor of healthy versus osteoporotic bone. However, the role of segmental contributing factors on VBQ is unknown. Methods. Nonsurgical patients who underwent repeated lumbar magnetic resonance imaging scans, at least three years apart primarily for low back pain were retrospectively included. VBQ was assessed as previously described. DD was assessed using the Pfirrmann grading (PFG) scale. PFG grades were summarized as PFGL1-4 for the upper three lumbar disk levels, as PFGL4-S1 for the lower two lumbar disc levels, and as PFGL1-S1 for all lumbar disc levels. Multivariable linear mixed models were used with adjustments for age, sex, race, body mass index, and the clustering of repeated measurements. Results. A total of 350 patients (54.6% female, 85.4% White) were included in the final analysis, with a median age at baseline of 60.1 years and a body mass index of 25.8 kg/m2. VBQ significantly increased from 2.28 at baseline to 2.36 at follow-up (P = 0.001). In the unadjusted analysis, a significant positive correlation was found between PFGL1-4, PFGL1-S1, and VBQ at baseline (P < 0.05) that increased over time (P < 0.005). In the adjusted multivariable analysis, PFGL1-4 (β = −0.0195; P = 0.021), PFGL4-S1 (β = −0.0310; P = 0.007), and PFGL1-S1 (β = −0.0160; P = 0.012) were independently and negatively associated with VBQ. Conclusions. More advanced and long-lasting DD is associated with lower VBQ indicating less bone marrow fat content and potentially stronger bone. VBQ score as a marker of bone quality seems affected by DD.